The present invention relates to machine tools and, more particularly to a high speed device for automatically machining a non-circular workpiece to a predetermined form. Still more particularly, the present invention relates to a high speed device for machining a non-circular workpiece that is controlled by a numerical controller or computer.
One type of conventional device for machining a non-circular workpiece generally requires a model of the required type and profile of the workpiece to be prepared to be installed in the device for replication in the machine tool. This method, commonly called the pantograph method, requires that a precise model of the workpiece be made for each new required shape. In addition, because the models are closely traced by a stylus during the machining process, they are subject to wear and must be replaced periodically. The constant modelling and replacement of the model required in this type of machine therefor requires considerable time and labor.
Inaccuracies inherent in the use of models to control the machining of the workpiece due to delays in positioning the cutting tool also require extensive and labor consuming rework of the machined workpiece.
A second type of device for machining non-circular workpieces employs lead screws that are controlled by a numerical controllers. This type of device is also subject to inaccuracies because the lead screws for positioning the cutting tool against the workpiece are subject to small amounts of end play. Such end play result in machining errors as the lead screws change rotational direction to move the cutting tool in and out. Such errors may be corrected later, or may result in scrap. Labor for correction and wasted scrap increase costs.